Recovery of ammonia from gas.



PATENTED MAR. 5, 1907,

. H.. KOPPERS. RECOVERY OP AMMONIA FROM GAS.

APPLICATION FILED SEPT. 2. 1905.

HEINRICH KOPPERS, OF ESSEN-ON-THE-RUHR, GERMANY.

nECovERYioF AMMoNlA FROM GAS.

Specification of Letters Patent.

Patented March 5, 1907.

Application filed September 2,1905. Serial Not 276,906.

Tol all whom it may concern:

Be it known that I, HEINRICH KoPPERs, a citizen of the German Empire, and a resident of Essen-on-the-Ruhr, Germany, have invented certain new and useful Improvements in and Relating to the Treatment of Gases Obtained from the Dry Distillation or'Gasiication ofv Fuels, of which the following is a specification.

The present invention has for its object to obtain the by-products contained in the frases of the dry distillation or gasification of fuels-that is to say, tar and ammonia-in a more simple and less costly manner than hitherto, purely and quantitatively, and at the same timeto avoid the waste liquids.

The invention is characterized mainly by the fact that the separation of these products from the gas mixture takes place at the degree of temperature which is most appropriate for obtalning them in the desired marketable condition and also that the waste waters are discharged into the atmosphere in a highly-diluted form. The method of procedure adopted is based upon observations and experiments .carried out and is normally as follows: The raw gas is greatly cooled in some'cases far below its dew or condensation tar-separator, mwhich the tar which has not yet been deposited is separated almost completely as a pure undccomposed mass. The temperature of the gas so purified is then raised to such an extent that it is superheated in accordance with the water that it contains. This heating of the gas is best effected by employing it as cooling medium in one of the coolers for the raw gas coming from the furnace, whereby the excess heat of this latter gas is indirectly transferred tothe former.

This gas, freed from tar, may then be washed with acid in known a pliances, thereby forming a concentrated liquor, as Owing to the superheating of the gases the water-vapors contained therein are also superheated. The

superheated vapors will not become conthe acid treatment, so that the liquor forme is not diluted by any condensation of water. That uantity-of water which is deposited owing to t edecrease of temperature of thegases and which contains about one-half the total quantity of ammonia, and in this all that ammonia which has already 'been neutralized in the raw gases by acidssuch as sulfuric acid or hydrochloric acid, for example, (up to ten per cent. of the total quantity)-is now advantageously further treated by itself. Fr example, it is driven ofi' in a separate distillation apparatus of any appropriate construction with lime and steam. The Waste gases therefrom, which contain the whole ammonia' and which have a temperature of 100 centigrade, enter a saturationvat which is filled with the liquor produced by washing the gases. It is possible to regulate this quantity proportionately, according as more or less water 1s sent over the distillation apparatus.

In rinci le the formation of the ammoniaca salt fiom the ammonia of the va ors and the sulfuric acid of the bath takes p ace at any temperature. However, fixed solid marketable ammonia (which is the desired iinal product) is only formed when the vapors passing through are superheated-that 1s to say, when no condensation, but, on the contrary, a further vaporization is effected upon entering the bath. The height of this temperature or the percentage of water is ascertainable from the consideration that ammonium lsuliate decomposes in neutral solution at temperatures of about 100 centigrade. The lower the temperature in the saturation-bath the less is the danger of small quantities of salt being volatilized from the salt solution. As the waste vapors form a su erheated mixture, the formation of the fixev sulfate takes place with certainty in the saturation-bath with acid-sulfate liquor, which is itself preferably maintained at an appropriate temperature, so as to avoid any condensation.

The Waste waters of the distillation apparatus invariably. contain dissolvedtar constituents, es ecially phenols, andare therefore harmfu They present dilute carbolicacid solutions which destroy everything. As the prejudicial substances, such as phenols, cannot be precipitated, these Waste waters cannot be purified by chemical means. Now in accordance with the process described above by avoiding the introduction of large l densed during quantities of fresh water in the process of 0btaining the by-products the quantity of these waste materials has already been considerably restricted, as the quantity of liquid remaining over is composed of the moisture contained in the coal (fourteenper cent. of the charge) and oi water chemically formed in the distillation, (six per cent. of the charge.) In order to render these quantities of li uid harmless in discharging them freely by iluting as much as possible'with water, it would be necessary to employ enormous quantities of water.

In accordance with the present process these waste products, which cannot bedestroyed chemically, are discharged for suitable dilution into the other medium which is available-that is to say, into the atmoshere, which is unlimited in amount. vThis 1s ei'lected by supplyin the waste waters of tlie distillation apparaus after clariication to the combustion-gases in the chimney, (in averyiinely divided state,).so as to vaporize and conduct them into the atmosphere.

The above-described process maybe carried out in the apparatus shown in the accompanying drawing, in which- Figures 1 and'2 represent a side elevation of the same, Fig. 2 being the right-hand continuatio'n of Fig. 1.

The hot raw gases of a coke or similar oven enter, through a pipe a, the space surrounding the tubes of a cooler b and pass through a pipe 'c into the corresponding'space of a second cooler d. A pump gl draws the cooled gases through pipe f from cooler d and conveys the same into a tar-separator h. The gases so freed from tar enter the tubes of cooler d through pi e t and travel thence through pipe 7c into t e tubes of cooler b. In coolers b and cl the temperature of the gases is again raised by the hot gases entering through pipe a and surrounding the tubes. After the gases have thus been treated they pass through ipe Z into an acidtower m. The latter is fi led with coke or similar material, which is continuously showered with acid. The gases thus freed from ammonia are conducted, through pipe o', into acooler p and are then adapted for further use.

The ammonia, which in the raw gas is combined with acid, is absorbed in cooler d, together with the water, the liquid separated in b and d being conveyed, through pipe q, into receptacle r, and thence into a distil1ation apparatus s. In the latter the liquid is driven off with lime and. steam, the gases thus generated flowing through pipe t into a saturation bath u. The latter is iilled, throughpipe v, with the liquor formed in acidtower m. The ammonium sulfate, which accumulates at the bottom of receptacle u, is continuously withdrawn from the latter by an ejector w or other suitable means. The spent liquor in distillati on apparatus s is led throu h pipe w', havin@ spraying-nozzle y, into c iimney the draft in the latter being maintained by blower z.

The possibility of carrying the process characterized above into practice industrially, owing to the quantities of free heat resent in the process, is shown by examining the theoretical data.

One ton of coal gives three hundred cubic meters of distillation-gas or eighteen hundred cubic meters of combustion-gas. Now one ton of coal furnishes two hundred kilograms of Water, so that 0.11 of a kilogram of water corresponds to one cubic meter of combustionegas. Now one cubic meter of combustion-gas at 3000 centigrade contains 1.2

800.0.23-that is .to say, approximately eighty-three thermal units. One hundred and ten gramsof water at centigrade re quire about sixty-five thermal units forcenverting them into steam. The atomization of water in the combustion-gas results in complete vaporization or superheating, and accordingly in complete removal.

It is true that the chimney-draft will be' By providing a 4 impeded to some extent. blower or similar apparatus, however, it may be restablished, so that the chimney may be regarded as a means for vaporizing these vapors and conducting them. away.

In addition to the waste heat of the combustion-gases passing off other quantities of heat which are liberated in coking, but which are never or seldom used, may likewise be employed in this vaporization. Thus, for example, the heat of the oven lost by radiation and the heat contained in the hot distillation-gases may be used.

The vapors of the saturation-bath freed from ammonia ass off in the hot gas coming from the scrub ers and are cooled with this latter to atmospheric temperature, when for the first time the water-vapors are completely deposited, this condensate forming a pure water fit for use. The gases themselves do not suffer in this process, so that from them benzol, illuminating-gas, and the like maybe formed, as usual. i

The process of obtaining ammonia and tar from gas which consists in cooling the gas to form cooled gas and a condensate, separating the tar from the cooled gas, superheating the gas freed from tar, washing the gas with acid to form a liquor, and mixing said liquor ina IOO lIO

IIS

IZO

saturation-bath with the Waste vapors ob- HEINRICH KOPPERS.

Witnesses WILLIAM EssENwEIN, ERNEST ANDR. 

